Surfacing disk



Patented Sept. 18, 1928.

UNITED Esra TfEis'PATENT osr cs.

HERBERT B. STRATFORD, OI CLEVELAND, OHIO, ASSIGNOR TO THE STRATMORE COM- PANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO SURFAO'HTG 'DISK.

No Drawing.

The present invention, relating as indicated to surfacing disks, is particularly directed to a new and improved disk formed of a single material and intended for use in the surfacing, grinding and finishing of various panels and articles, such as sheet metal panels for use in automobile bodies, castings, machined articles and others. The principal object of the invention is the provision of a disk for'the'purposes refer-red to which shall be simple and inexpensive to manufacture, and which shall be formed of one or more layers of a single material. A further object of the invention is the pro vision'of a .disk which shall have an increased life and an improved bond between the surfacing material, such as abrasive, the

elements which constitute the disk proper, such as the layer or layers of supporting material.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims; the following description setting forth in detail certain mechanism embody-- ing the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

Abrasive paper, such as sand paper, emery paper and the like, has long been used and consists of a layer of grains of a suitable abrasive secured, by means of an adhesive such as glue, varnish or the like to a supporting backing formed of some light paper. In the use of such papers neither flexibility nor strength in any unusual degree was reuired or secured, but upon the introduction of machine grinding in which disks are mechanically driven to simulate or to improve upon the condition secured by grinding wheels, it is found necessary, in order to secure a suitable strength of materialgand a bond between abrasive and backingyrto reinforce the paper disk with a layer of cloth which was usually interposed between the gaper element and adhesive and abrasive. y means of this combination of materials a suitable flexibility in the disk was secured while still retaining a suflicient strength and resistance to buckling to permit such disks in some cases to be driven under very severe conditions from the center, while atthe safne time a strong bond was obtained between Application filed December 31, 1927. Serial 116. 244,052.

the abrasive and the disk through the penetration of the adhesion in the cloth. This bond was sufliciently effective to prevent the early removal of the grains from the disk even at those portions of the disk in which repeated flexing was taking place.

Many millions of composite disks of the character described above have been made and used to a great .advantage in grinding and finishing operations on all sorts'of, surfaces, the only objectionable feature of. such disks being that they were expensive and difficult to manufacture. I have discovered that certain materials possessing certain characteristics may be employed without any reinforcing material and, contrary to the expectations and experience of experi enced manufacturers of abrasive, my new disk is capable of holding its abrasion, even at those points where repeated flexing is by treating cellulose with a material capable 1 of partially dissolving the cellulose, such for example as zinc chloride. In manufacturing this material old cotton rags are commonly employed as the raw material, these rags consisting of almost pure cellulose.

These are pulped and formed into sheets in the ordinary manner and the sheets are then passed through a zinc chloride solution causing the partial solution of the fibres, and probably the outside of each individual fibre is partially dissolved, producing a gelatinous, and more or less adhesive, coating on each fibre. The sheets thus treated are then again passed-through rolls to remove the excess zinc chloride solution and to compress the fibres tightly together. Subsequent treatment consists in removing the final traces of zinc chloride, which may be effected by washing the sheets with water, after which the sheets are hardened and dried. It will be understood that various other reagents may be employed instead of rotated at a speed betweenv 5000 and 10,000.

the zinc chloride, provided that they also have a gelatinizing of parts of the fibres to produce a chemical and mechanical adhesion etween the fibres during the treatment which is far more effective in cementing the entlre structure together than merely the ordinary mechanical adhesion secured through ressure in the ordinary paper stock. T e result of'this treatment of the material is to greatly increase the strength,

the density and the rigidity, and to lowerthe porosity .while producing a structure which has little or no tendency to split or curl. This product is ordinarily referred to as hydrolyzed cellulose, or commercially as vulcanized fibre.

I have found that a disk formed of a suitable layer of vulcanized fibre of certain characteristics when supplied with a coating ,on one surface of grains bonded thereto by a suitable adhesion will dry perfectly flat and without any curling or splitting of the edges, is, of almost precisely the desired flexibility and rigidity andpossesses a bond between abrasive and fibre which is suflicient to hold the abrasive in position even under the most severe service and for a length of time materially greater than the best composite disks of the paper stock and cloth which are at present in common use, and which u to this time have been universally concede to be the only type of disk capable of withstanding the extremely severe service to which these disks are put.

' It will be understood that in certain cases this type of surfacing disk is secured at itscenter to a supporting pad or cushion formed of various materlals, such as a layer of compressible material, such as felt, and a support behind the felt, such as a plate of metal, and is then rotated at extremely high speed while the radially outer portion of the abrasive disk is ressed firmly against a surface to be treate such for example as a rough metal panel of pressed steel. This operation is an extremely severe one, since at its outer edge the disk is sometimes being ft. per minute over a surface of extremely tough material which is being ground away by this'operation while the power applied to the disk for effecting the rotation is'applied at a point remote from the engagement etween the disk and the work, namely, at the center of the disk, a number of inches away from the point where the disk engages the panel. In addition tothe torsional strains imposed on the disk between the center and the edge there is also an additional strain imposed on the material when, as is frequently the case, the disk is running over a projecting weld or bend in the panel, which is thus causing the disk to flex back and forth at a speed some times in excess of 3600 flexures per minute. It is this flexing back vwhich is resisted, but permitted to a certain extent, bythe compressible supporting pad, against which the disk is used.- It was because of this extremely severe service to which the disk is put that experienced abrasive manufacturers resorted to the expensive combination of a sheet of paper stock and a sheet of fabric to build up a com posite disk which wasexpected to have, to a maximum degree, the particular characteristics of flexibility, torsional strength and ability to retain the bond between the abrasive grains and the cloth required in such an article.

I have found that a very much superior disk can be formed from one or more layers of vulcanizedfibre, depending upon the particular service to which the disk-is to be put, since a disk of this material has, in a high degree, the particular qualities or characteristics which various tests have indicated are the determining factors in the success of the composite disk, although these characteristics are either present to a greater degree in a disk of fibre alone, or certain other characteristics which detract from the life of a composite disk are missing from a disk of fibre alone.

One desired characteristic which is apparently' important and necessary in such a disk is that the disk be of dense material. Thus, the density should be such that the weight of the material per cubic centimeter should be one gram or more.

The tensile poun s longitudinally of the sheet of paper from which the disk is to be formed and 85 t pounds transversely. I Resistance to abrasion is of considerable importance and tests show that thematerial employed should not lose more than 15 per centby weight when abraded with an aloxite disk operated against asheet of the material under a pressure of of a pound for .100 revolutions. A further characteristic which I consider to .be of considerable importance is the abilit of' the material to withstand rupture.

y improved disk is capable of withstanding rupture when a piece one foot square is clamped in a frame and a four-pound weight allowed to drop a ainst the paper through a distance of four eet.

The improved life of my new disk formed of the vulcanized fibre is also believed to be the abrasive from the rotating edge of the disk and the pressing of this edge portion 1 struction of the disk. In my'preseiit disk,

the grains when removed from the paper leave the paper, or rather the vulcanized fibre, which is then pressed against the work but which is not capable of being stretched as is the cloth, and hence does not transfer strains to the adjacent operating portions of the disk. I believe that thisdifi'erence between the composite and the unit disks accounts in a large part for the increased life of the present construction, and thereby presents the anomaly of a disk of supposedly Weaker and less rigid construction having a materially longer life than a disk ofsupposedly strong, tough and rigid construction.

The particular advantages of my improved disk may also be secured in a disk'formed of two adhesively joined sheets of relatively -thin fibre, to the outer surface of one of which the abrasive is then bonded as before. Similarly, the same advantages may be secured either wholly or in part by adhesively binding together a relatively thin layer of fibre and a layer of some other material, such, for example, as pattern board. In this (Ltly contact-12t erwisebe my invention may be employed one explained, change being made as regards the mechanism herein disclosed, provided the required of such a disk, while the other sheet of different material acts as a reinforcing andma'y be built up in thickness to secure, in combination with the fibre sheet, the other properties {which have been found necessary in such disk.

Other modes of applying the principle of instead of the means stated by any of the following claims or the equivalent of such stated means be employed.

' s I therefore particularly point out and distinctly claim as my invention 1. A surfacing element consisting of a sheet of hydrolyzed cellulose having a density ofnot less than one gram per cubic centimeter, and carrying a layer of grains adhesively secured to one surface thereof.

2. A surfacing element consisting of a sheet of cellulose material provided with a layer of abrasive grains adhesively secured to one surface of said sheet, and the latter having a tensile strength of not less than 170 pounds per square inch in one direction and of not less than 85 pounds per square iiinch in a direction at right angles to the rst.

Signed by me, this 29 day of December,

HERBERT R. STRATFORD. 

